Static contact angle algorithm selection for superhydrophobic surface hydrophobicity detection

Abstract

The static contact angle calculation for superhydrophobic surfaces is systematically investigated. The water drop profiles with different volumes, contact angles, rotational angles and apex coordinates are numerically generated based on the Laplace equation. Thereafter, the goniometry, θ/2 method, circle and ellipse fitting algorithms and an improved axisymmetric drop shape analysis-profile (ADSA-P) algorithm are used to calculate the static contact angle. The results reveal that the contact angle errors by the θ/2 method, circle and ellipse fitting algorithms increase with the drop volume/contact angle. The goniometry will introduce significant error. The ADSA-P algorithm can accurately obtain the contact angles (error < 0.3°) for the drop profiles regardless of the water drop volume, contact angle, rotational angle and apex coordinate. The ADSA-P algorithm should be selected to calculate the static contact angles for the superhydrophobic surfaces. Static contact angle measurements of the superhydrophobic surfaces validate the aforementioned analysis.